Still haven't seen Matt Smith's Doctor, but I plan to pretty soon here.
I do agree that the new series has a VERY different feel from the old one, but because I started with the new (but was familiar with the old at the same time), I didn't mind it. I still don't. The show even changed from era to era with each of the different Doctors, and I enjoy the differences across all of them. Yes, even Colin Baker's era (GOD what a shame the writers couldn't figure out his Doctor...).
I think Tennant's run benefited most from having time to really develop his version of the Doctor and have him change over time. You got to see him gradually fall in love with Rose, then lose her, deal with the fallout, be COMPLETELY clueless about Martha digging him (actually....I don't think clueless. I think he knew...and kind of needed it at the time...), get to become good friends with Donna, and then lose EVERYTHING (including his mind) only to finally pull it together at the end and save both the universe and himself one last time, thereby finding a kind of redemption and peace.
And then came Matt. Who, as I said, I still haven't seen.
I don't think the other Doctors enjoyed quite that level of coordinated writing, and as a result, their eras explore their characters gradually, and often only in bits and pieces. Heck, during Hartnell's era, the Doctor was a TOTAL mystery. We don't realize it, but they knew NOTHING about his background during that time. It wasn't even 100% clear if he was human or an alien, let alone any mention of what the Time Lords were. It isn't really until the finale of The War Games that a lot of the lore starts to develop, and then I don't think we even see Gallifrey until Tom Baker's era. Now, of course, we have this whole lore that's developed around the Doctor, but it wasn't always that way because, I suspect, they didn't often know where they were going with the character. In fact, I gather that it wasn't until Sylvester McCoy's era that the concept of some overarching mythology to drive the Doctor was established, as if it'd eventually be revealed. (Setting aside the whole Key to Time and Black Guardian seasons for the 4th and 5th Doctors.) And, of course, it never WAS really clearly revealed, so we never found out, for example, that the Doctor was actually one of the founders of Gallifreyan society.
Ah well.
Anyway, I dig all the eras, albeit some more than others (I FAR prefer "brown" 4th Doctor to "maroon" 4th Doctor, and am less of a fan of the JNT years than other years).